(R¹, R², R³ and R⁴: the same or different, H, NO₂, CN, Halo, a hydrocarbon group which may be substituted, a heterocycle which may be substituted, a hydroxy which may be substituted, a carboxy which may be substituted, an acyl-O— which may be substituted, an acyl which may be substituted, a substituent —S(O)n₁₀₁— (n₁₀₁: an integer of 0 to 2, the same shall apply hereinafter), H—S(O)n₁₀₁—, a carbamoyl which may be substituted, a sulfamoyl which may be substituted, or an amino which may be substituted, and two adjacent groups selected from the group of R¹, R², R³ and R⁴ may be combined to form an aryl or a cycloalkenyl; R⁵ and R⁶: the same or different, H, Halo, a hydrocarbon group which may be substituted or an amino which may be substituted; X¹ and X²: the same or different, N, S or O atom; A and B: the same or different, an aryl which may be substituted or a heterocycle which may be substituted; Z¹, Z², Z³ and Z⁴: C or N; provided that 1) when X¹ and X² each is S or O, one or both of the corresponding R⁵ and R⁶ are absent; 2) when one to four of Z¹, Z², Z³ and/or Z⁴ are N, the corresponding R¹, R², R³ and/or R⁴ are absent; and 3) that if one of A and B is phenyl, the other is not 4-nitrophenyl)

or a pharmaceutically acceptable salt thereof, provided that the compounds 1 to 39 shown in the following table are excluded, wherein the symbol Ph means phenyl, Me means methyl, Et means ethyl, and tBu means tert-butyl,